The present invention relates to flow meters, more particularly to devices capable of measuring the flow of liquids with large variations in viscosity.
There are various types of known flow meters or sensors, for example those using differential pressure or area to measure the flow, volume measuring devices, mass flow meters and rotating body type devices. U.S. Pat. Nos. 2,518,149 and 3,805,609 show flow meters of the rotating body type in which a swirling stream of fluid is used to rotate a body in the swirling stream path, the rotation of the body giving a measurement of the flow rate.
The rotating body type of flow meter, as well as the differential pressure and area types of device, are generally not very accurate with changes of viscosity, since they depend on directional forces for their operation. These forces change radically with changes in viscosity.
Volume measuring devices generally depend upon precision cylinders and usually will not measure continuous flow rate. They are expensive to manufacture and maintain. Mass flow meters are very expensive and generally will not handle a large variation in viscosity.